In respirator systems, distinction is made, in principle, between ambient air-independent and ambient air-dependent respirator systems. If the user is in an atmosphere with low oxygen concentration, the breathing air needed must be supplied continuously from a compressed air cylinder via a compressed air hose. If, by contrast, the surrounding atmosphere contains a sufficient quantity of oxygen, a light-weight, ambient air-dependent breathing system can be used, which is equipped with a special filter, which is adapted to the particular harmful substances present in the atmosphere to and the concentrations of these substances. The filters of such a system are usually mounted on a breathing mask or face mask via a screw thread, and this filter is designed to filter harmful dusts, gases or vapors, aerosols, etc., from the ambient air. However, it is also possible to use, as an alternative, filters that are provided separately from the mask and are connected with the mask via a breathing tube. These separate filters may be carried, for example, on the user's belt. The filters used differ from each other in terms of their fields of use, but they have basically the property of removing gases and vapors by absorbing them on sorbents (e.g., impregnated activated carbon) or particles and aerosols, for example, by a microfiber filter.
Ambient air-dependent respirator systems, which are provided or coupled with a filter (also called “Air-Purifying Respirator”=APR), are usually small, lightweight and easy to use. One drawback of these systems is, however, the fact that the user's breathing resistance and hence the user's breathing work is increased by the filter, as a result of which the performance of the user in action is compromised in an undesired manner. To overcome this drawback, filter-type breathing systems were developed, which are provided with a blower unit, and which are also called blower-assisted respirator systems or blower filter systems (Powered Air-Purifying Respirator=PAPR) and by means of which the user's breathing work is markedly reduced. These systems comprise essentially a breathing mask (or face mask or hood), which is provided with a breathing port (mostly a round threaded port) for connecting a breathing tube, and a blower unit, which contains a blower device, an energy supply unit and a filter insert for coupling a suitable filter. The blower unit (or blower system device) is preferably carried on the user's belt. Contaminated air is drawn in from the surrounding area in such a system by means of the blower unit, filtered by means of the coupled filter, as a result of which the contaminated air is freed from harmful substances, and blown through the breathing tube into the face mask.
The above-described blower filter systems are used, in general, for light and medium breathing protection. The advantage of these blower filter systems is that they support the user during breathing by lowering the breathing protection compared to conventional breathing masks and thus make long-term as well as fatigue-free use possible. However, these blower filter systems have some drawbacks. Thus, the user must carry not only the breathing mask but additionally also the blower filter system attached to the belt (blower unit). The entire system is thus relatively heavy and possibly unwieldy, which may affect the user's freedom of movement. This drawback is especially manifest when the system is designed for long operating times, and the blower filter system attached to the belt must therefor be equipped with a large number of batteries (secondary cells) and therefore becomes large, heavy and unwieldy.
The blower filter system contains, among other things, a blower impeller driven by an electric motor and a blower housing (e.g., a spiral housing) adapted to the blower impeller. The energy for this blower unit (i.e., for the electric motor and the corresponding central control unit) is provided by an energy supply unit, which preferably has rechargeable batteries (batteries or secondary cells). The motor of the blower unit is controlled by means of the central control unit. The control unit is further designed to process, for example, data input by the user. These input data comprised, for example, the switching on and off of the blower unit or the setting of the output of the blower unit. In addition, the control unit may be designed to adapt the output of the motor (or of the blower unit) to the user's requirements. This is especially important when the user needs more breathing or because of increased physical stress or when the breathing resistance through the filter increases after a prolonged operating time. The blower unit, control unit and energy supply unit are usually enclosed by a housing. At least one filter may be connected to this housing. As an alternative, the filter may, however, also be arranged within the housing. In addition, the breathing tube may be connected with one end to this housing, in which case the other end of the breathing tube is coupled with the breathing mask. Air is drawn into the housing of the blower unit by means of the blower device during the operation and is then sent to the face mask through the breathing tube connected to the blower unit. The face mask is provided with an exhalation valve for breathing out the consumed breathing air.
As was explained above, blower filter systems are used under greatly different ambient conditions. These may comprise ambient conditions under which the surrounding atmosphere contains potentially explosive gases or dusts. Special requirements are imposed on the components used in the blower filter systems in this case. Two reasons for a potential ignition must be ruled out in case of explosion protection: (1) Spark ignition, which may be induced by an energy released in case of a defect, must be avoided, and (2) self-ignition, which may be induced by overheating of components of the blower filter system, must be ruled out.
Blower filter devices or blower filter systems for use in potentially explosive areas are already known. However, battery packs (=energy supply unit), which contain nickel-metal hydride or nickel-cadmium cells, are used in these prior-art devices. To reach adequate operation times, a large number of cells must be connected together, as a result of which the weight of the device to be carried by the user increases markedly.